Method of manufacturing hollow blade and hollow blade manufactured by same

ABSTRACT

In injection-molding first and second blade bodies (2, 3), convex parts (23, 32) are formed on the surfaces of the first and second blade bodies (2, 3), respectively. Then, a horn (16) of an ultrasonic welding device is placed at a position of crossing both the convex parts (23, 32) to come into contact with the top surfaces of the convex parts (23, 32) while pressing them at the same time, and in this state, the ultrasonic welding device is operated. Contact surfaces of the first and second blade bodies (2, 3) are welded at their portions corresponding to a pressing direction of the horn (16) and concurrently, both the convex parts (23, 32) are deformed by melting under pressure through the horn (16) to trickle melting resin of both the convex parts (23, 32) into a clearance (10) between the first and second blade bodies (2, 3), so that both the blade bodies (2, 3) are joined to each other.

TECHNICAL FIELD

This invention relates to a method of manufacturing a hollow blade and ahollow blade manufactured by the method.

BACKGROUND ART

FIG. 7 shows one of procedures in a conventionally typically method ofmanufacturing a hollow blade. FIGS. 8 and 9 each show an essential partof a hollow blade 50 manufactured by the conventional method.

In the conventional method of manufacturing a hollow blade, a firstblade body 51 with a recessed part 53 and a second blade body 52 formedso as to close the recessed part 53 are first put together. Then, thefirst and second blade bodies 51, 52 are joined by welding by means of aultrasonic welding device thereby forming the hollow blade 50 internallyprovided with a hollow part 56 composed of a part of the recessed part53.

In this case, the first blade body 51 is provided with a shelf surface54 formed at an outer periphery of the recessed part 53. An outerperipheral part of the back face 52b of the second blade body 52 is laidon the shelf surface 54 of the first blade body 51 so that the secondblade body 52 is faced with the first blade body 51 in a partly contactstate. An outer peripheral end surface 51b between the shelf surface 54and the surface 51a of the first blade body 51 is opposed to an outerperipheral end surface 52c of the second blade body 52 with a set spaceleft, thereby creating a clearance 59 between both the outer peripheralend surfaces 51b, 52c.

In the state that the first and second blade bodies 51, 52 are facedwith each other in a contact state, a horn 60 of the ultrasonic weldingdevice is moved down from above the clearance 59. Thus, the end surface60a of the horn 60 is located at a position of crossing the first andsecond blade bodies 51, 52 interposing the clearance 59 therebetween andcomes into contact with both the blade bodies 51, 52 while pressingthem. In this state, ultrasonic vibrations are applied to the bladebodies 51, 52 by the horn 60 in its pressing direction (direction ofarrows a-b of FIG. 7).

Frictional heat resulting from the ultrasonic vibrations is producedbetween the shelf surface 54 of the first blade body 51 and the outerperipheral part of the back face 52b of the second blade body 52 whichcome into face-to-face contact with each other, and is also producedbetween each of the surfaces 51a, 52a of the first and second bladebodies 51, 52 and the end surface 60a of the horn 60 which come intoface-to-face contact with each other.

If frictional heat produced due to contact between resin materials iscompared with frictional heat produced due to contact between metal andresin, the former has a higher temperature. Accordingly, resin is morereadily melted at a part where the back face 52b of the second bladebody 52 is laid on the shelf surface 54 of the first blade body 51, sothat a resin melting part 55 shown in FIG. 8 or a first resin meltingpart 55A shown in FIG. 9 is produced. The first and second blade bodies51, 52 are joined to each other through the resin melting part 55 or thefirst resin melting part 55A.

On the other hand, on each of the surfaces 51a, 52a of the first andsecond blade bodies 51, 52, resin is softened through the application ofpressure and ultrasonic vibrations by the horn 60 so that a circularimpression 58 along the shape of the horn 60 is produced. As shown inFIG. 8, when the pressing force of the horn 60 is set smaller so as toreduce the depth of the impression 58 as small as possible, an amount ofmelting resin produced by the formation of the impression 58 isdecreased. As a result, an amount of flow of the melting resin into theclearance 59 is also decreased so that the clearance 59 is substantiallykept in its original state.

On the contrary, when the pressing force of the horn 60 is increased,the depth of the impression 58 becomes larger as shown in FIG. 9, sothat the amount of meltingresin produced accompanying the formation ofthe impression 58 is increased. As a result, a part of the melting resinflows into the clearance 59 so that a second resin melting part 55B isformed at an upper portion of the clearance 59. The second resin meltingpart 55B joins the first and second blade bodies 51, 52 to each other.

The joint strength between the first and second blade bodies 51, 52 ismainly ensured by the resin melting part 55 (in the case of FIG. 8) orthe first resin melting part 55A (in the case of FIG. 9). However, whenboth the blade bodies 51, 52 are also joined to each other through thesecond resin melting part 55B as shown in FIG. 9, the joint strengthbetween both the blade bodies 51, 52 is increased, which is preferablein point of joint strength.

Problems to be Solved

Since the joint strength between the first and second blade bodies 51,52 is mainly ensured by the resin melting part 55 (in the case of FIG.8) or the first resin melting part 55A (in the case of FIG. 9) asmentioned above, the resin melting parts 55, 55A must be surely formedin order to ensure reliability on the manufacture of the hollow blade50. In other words, it is necessary to check, in a quality inspectionafter the manufacture, that the parts in question have been subjected towelding by the ultrasonic welding device.

In this case, a particular need for mass production of the hollow blade50 is that the quality inspection can be made with efficiency andreliability.

However, since the resin melting parts 55, 55A are located inside thehollow blade 50, the inspector cannot make a direct visual check of themfrom outside. Therefore, in order to perform the quality inspection ofthe hollow blade 50 with efficiency and reliability, it is necessarythat a visual check of the resin melting parts 55, 55A can be made bythe inspector even though it is in an indirect manner.

In the case of the hollow blade 50 manufactured by the conventionalmanufacturing method, the impression 58 can be an object of the visualcheck.

Next, a consideration will be given to the hollow blade 50 manufacturedby the conventional manufacturing method shown in FIGS. 8 and 9.

In the hollow blade 50 shown in FIG. 8, the depth of the impression 58produced on the surfaces 51a, 52a of the first and second blade bodies51, 52 is reduced as small as possible. Accordingly, when the qualityinspection is performed through a visual check of the impression 58, itis difficult to recognize the impression 58 and, in some cases, it maybe difficult to judge whether a welding work has been made or not.Accordingly, the above-mentioned hollow blade 50 has a problem in pointof efficiency and reliability of the quality inspection.

In the hollow blade 50 shown in FIG. 9, since the depth of theimpression 58 is large, a visual check of the impression 58 can be madewith ease and reliability, which makes the hollow blade 50 of this caseseem preferable in point of efficiency and reliability of the qualityinspection. Further, since the second resin melting part 55B is formedat the upper portion of the clearance 59, the hollow blade 50 of thiscase has an advantage in its increased joint strength.

However, when an impeller is formed of the hollow blades 50 with such animpression 58 having a large depth, it can be considered that largenoise is produced at the position of the impression 58 in associationwith the rotation of the impeller, which is not preferable.

In addition, the formation of such an impression 58 having a large depthsqueezes a part of melting resin out of the impression 58 in a radialdirection, thereby forming a swelling 57 around the impression 58. Sincethe swelling 57 results in production of noise if it is left, it isrequired to be removed. This increases the number of manufacturingsteps, which is an undesired effect.

The present invention has been made in view of the foregoing problemsand therefore, has its object of providing a hollow blade on which aninspection for a joint work can be performed with efficiency andreliability through a visual check from outside while the smoothness ofthe blade surface is maintained and providing a method of manufacturingthe hollow blade.

DISCLOSURE OF INVENTION

To solve the above problems, the present invention takes the followingmeasures.

A first invention premises a method of manufacturing a hollow bladewhereby first and second resin-made blade bodies formed by injectionmolding are put together and are joined by welding by means of anultrasonic welding device to form a hollow blade internally providedwith a hollow part.

First, in injection-molding the first and second blade bodies,respective convex parts swelling from respective surfaces of the firstand second blade bodies are formed at positions contiguous with andopposed to each other when both the blade bodies are put together.

Next, in joining the first and second blade bodies to each other by theultrasonic welding device, a horn of the ultrasonic welding device isplaced at a position of crossing both the convex parts to come intocontact with the top surfaces of the convex parts while pressing them atthe same time and in this state the ultrasonic welding device isoperated.

Then, contact surfaces of the first and second blade bodies which extendin a direction approximately orthogonal to a direction of puttingtogether both the blade bodies are welded at their portionscorresponding to a pressing direction of the horn, and concurrently,both the convex parts are deformed by melting under pressure through thehorn to trickle melting resin of both the convex parts into a clearancebetween the first and second blade bodies so that both the blade bodiesare welded in a manner of forming a bridge therebetween, thereby joiningboth the blade bodies into one piece to form a hollow blade.

A second invention is so composed that in the first invention, an amountof deformation of each of the convex parts through the application ofpressure by the horn is set at a value approximately identical to theheight of the convex part.

A third invention premises a hollow blade in which first and secondblade bodies are put together to form a hollow part therebetween.

The first and second blade bodies in a state of being put together arejoined by welding at their contact parts and their opposed parts forminga clearance created when the first and second blade bodies are puttogether.

A fourth invention is so composed that in the third invention, a weldedpart at the clearance between the first and second blade bodies isformed such that the surface thereof is approximately flush with thesurfaces of the first and second blade bodies.

Effects of the Invention According

According to the first to fourth inventions above-mentioned, thefollowing effects can be obtained.

According to the first invention, respective convex parts are providedon respective surfaces of the first and second blade bodies ininjection-molding both the blade bodies, the first and second bladebodies are welded at their contact parts, and melting resin of both theconvex parts are concurrently trickled into a clearance between thefirst and second blade bodies so that both the blade bodies are welded.Accordingly, a joint work can be verified by a visual check of thedeformation of the convex parts.

In detail, in joining the first and second blade bodies to each other bythe ultrasonic welding device, convex parts previously provided on thefirst and second blade bodies are deformed under pressure. Accordingly,after the hollow blade is manufactured, a visual check is made on thestate of deformation of the convex parts as compared with the state ofthe convex parts before manufacturing the hollow blade, therebyverifying that a joint work by means of the ultrasonic welding devicehas been performed.

In other words, a resin melting part is surely formed on the contactsurfaces of the first and second blade bodies inside the hollow blade,and the joint of both the blade bodies through the resin melting partcan be verified with ease and reliability. As a result, apost-manufacturing quality inspection of the hollow blade can secureefficiency and reliability.

Further, the convex parts are melted and the melting resin thereof istrickled into the clearance between the first and second blade bodies bythe horn, so that a resin melting part is formed in the shape of abridge between both the blade bodies. Thereby, the first and secondblade bodies are also joined at an upper portion of the clearancethrough the resin melting part, which further increases joint strength.

According to the second invention, since an amount of deformation ofeach of the convex parts through the application of pressure by the hornis set at a value approximately identical to the height of the convexpart, the blade surface has no unevenness when the convex parts aredeformed under pressure, which maintains the excellent smoothness of theblade surface.

According to the third invention, since the first and second bladebodies in a state of being put together are joined by welding at theircontact parts and their opposed parts forming a clearance created whenthe first and second blade bodies are put together, the joint strengthbetween both the blade bodies is higher as compared with the case thatboth the blade bodies are joined by welding only at their contact parts,which increases the reliability in using the blade.

According to the fourth invention, since a welded part at the clearancebetween the first and second blade bodies is formed such that thesurface thereof is approximately flush with the surfaces of the firstand second blade bodies, noise when an impeller formed of the first andsecond blade bodies is run can be reduced to a minimum in contrast tothe conventional case that an impression is left on the blade surface,thereby realizing a quiet run of the impeller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a hollow blade manufactured by amanufacturing method of this invention.

FIG. 2 is a cross-sectional view taken on line II--II FIG. 1.

FIG. 3 is an enlarged view of a part III of FIG. 2.

FIG. 4 is a view taken in the direction of arrows IV--IV of FIG. 3.

FIG. 5 is a cross-sectional view showing a process of manufacturing thehollow blade.

FIG. 6 is a view taken in the direction of arrows VI--VI of FIG. 5.

FIG. 7 is a cross-sectional view showing a conventional method ofmanufacturing a hollow blade.

FIG. 8 is a cross-sectional view showing a hollow blade manufactured bythe conventional manufacturing method.

FIG. 9 is a cross-sectional view showing a hollow blade manufactured bythe conventional manufacturing method.

BEST MODE FOR CARRYING OUT THE INVENTION

Below, a detailed description is made about an embodiment of the presentinvention with reference to the drawings.

FIG. 1 shows a hollow blade 1 manufactured by a manufacturing method ofthe present invention. FIG. 2 shows a sectional form of the hollow blade1.

A plurality of such hollow blades 1 are fixed to a boss 7 therebyforming an impeller. As shown in FIGS. 1 and 2, the hollow blade 1 isformed into a plane having an approximate trapeziform outline and isinternally provided with a hollow part 5 extending along the plane. Thehollow blade 1 is manufactured by putting together first and secondblade bodies 2, 3 and joining them.

The first blade body 2 is previously formed into a set shape byinjection molding with the use of a resin material prior to a joint workbelow-mentioned. The shape is as follows: as shown in FIGS. 1 and 2, thefirst blade body 2 is formed into a plane having an approximatetrapeziform outline; the surface 2a of the first blade body 2 forms theback face If of the hollow blade 1; and the back face 2b of the firstblade body 2 is provided with an approximate trapeziform recessed part 4which is recessed on the surface 2a side along the outline of the firstblade body 2.

As shown in FIGS. 3 and 5, a peripheral edge of the recessed part 4 isprovided with a shelf surface 22 which is located slightly above thebottom of the recessed part 4 and extends along the plane of the firstblade body 2, and is provided with an outer peripheral end surface 21rising along the outer peripheral edge of the shelf surface 22. Thefirst blade body 2 has an integrally-molded blade fixing part 11 whichserves as a part for fixing the first blade body 2 to the boss 7.

Similarly to the first blade body 2, the second blade body 3 ispreviously formed into a set shape by injection molding with the use ofa resin material prior to the joint work. The shape is as follows: asshown in FIGS. 1 and 2, the second blade body 3 is fitted on therecessed part 4 of the first blade body 2 so as to cover it and isjoined to the peripheral edge of the recessed part 4; the second bladebody 3 is formed into a plane having an approximate trapeziform outlineso as to conform to the outline of the recessed part 4; and the surface3a of the second blade body 3 forms a part of the surface 1e of thehollow blade 1.

In a state that the second blade body 3 is fitted on the recessed part 4of the first blade body 2 and the first and second blade bodies 2, 3 areput together (See FIGS. 1 and 2), the outer peripheral part of the backface 3b of the second blade body 3 comes into face-to-face contact withthe shelf surface 22 provided on the recessed part 4 of the first bladebody 2. Thus, the shelf surface 22 of the recessed part 4 of the firstblade body 2 and the outer peripheral part of the back face 3b of thesecond blade body 3 form a contact surface and a contact part,respectively. Further, in the above state that both the blade bodies 2,3 are put together, the outer peripheral end surface 21 of the recessedpart 4 is opposed to an outer peripheral end surface 31 of the secondblade body 3 with a set space left therebetween. Furthermore, betweenboth the outer peripheral end surfaces 21 and 31, an annular clearance10 is formed so as to extend along the outline of the recessed part 4.

Further, the first and second blade bodies 2, 3 are provided with convexparts 23, 32 characterized in the present invention, respectively.

As shown in FIGS. 5 and 6, the convex part 23 has an approximate halfcolumnar shape and is formed on the back face 2b of the first blade body2 which forms a part of the surface 1e of the hollow blade 1. Aplurality of the convex parts 23 are provided along the peripheral edgeof the recessed part 4. The convex parts 23 are integrally formed withthe first blade body 2 in such a manner as to swell parts of the firstblade body 2 to a set height when the first blade body 2 isinjection-molded. In this embodiment, seven convex parts 23 are providedas shown in FIG. 1.

On the other hand, as shown in FIGS. 5 and 6, the convex part 32 has anapproximate half columnar shape, similarly to the convex part 23, and isformed on the surface 3a of the second blade body 3 which forms a partof the surface 1e of the hollow blade 1. A plurality of the convex parts32 are provided along the peripheral edge of the recessed part 4.

As shown in FIG. 1, the positions where the convex parts 32, 32, . . .of the second blade body 3 are to be formed are set to correspond to thepositions of the convex parts 23, 23, . . . of the first blade body 2,respectively. The convex parts 32 are integrally formed with the secondblade body 3 in such a manner as to swell parts of the second blade body3 to a set height when the second blade body 3 is injection-molded.

Thus, as shown in FIG. 1, the convex parts 23, 23, . . . of the firstblade body 2 are contiguous with and opposed to the convex parts 32, 32,. . . of the second blade body 3, respectively, when the first andsecond blade bodies 2, 3 are put together.

In the state that the convex parts 23 are opposed to the convex parts32, respectively, the first and second blade bodies 2, 3 which are puttogether are subjected to a joint work by means of an ultrasonic weldingdevice thereby forming both the blade bodies 2, 3 into one piece. Thisformation of a one-piece structure provides a hollow blade 1 internallyprovided with the hollow part 5 formed of the recessed part 4.

Joint Work

Next a description will be given to the joint work by means of theultrasonic welding device.

As shown in FIG. 5, a horn 16 attached to an oscillator 15 of theultrasonic welding device is placed above a pair of the convex parts 23,32. The end of the horn 16 is made contact with the top surfaces of theconvex parts 23, 32 and a specified pressing force is applied to theconvex parts 23, 32. In this state, ultra sonic vibrations in adirection of applying the pressing force (direction of arrows a-b ofFIG. 5) are given to the convex parts 23, 32 through the horn 16.Through the application of ultrasonic vibrations, frictional heat occursat an interface between the shelf surface 22 of the first blade body 2and the outer peripheral part of the back face 3b of the second blade 3so that the interface is melted thereby forming a first resin meltingpart 41 as shown in FIG. 3. Through the first resin melting part 41, thefirst and second blade bodies 2, 3 are joined in the vicinity of a lowerend of the clearance 10.

Meanwhile, frictional heat also occurs between each of the convex parts23, 32 and the horn 16, so that the convex parts 23, 32 are melted.Melting resin thus obtained trickles into an upper part of the clearance10 by the capillary action of the clearance 10 and the pressing actionof the horn 16. Thus, as shown in FIGS. 3 and 4, a bridge-like secondresin melting part 42 is formed at the upper part of the clearance 10 soas to cross the outer peripheral end surface 21 of the first blade body2 and the outer peripheral end surface 31 of the second blade body 3.Through the second resin melting part 42, the first and second bladebodies 2, 3 are joined at the upper part of the clearance 10.

Effects

As mentioned so far, according to this embodiment, since the first andsecond blade bodies 2, 3 are joined to each other in the vicinity of thelower end of the clearance 10 as well as at the upper part of theclearance 10, joint strength can be increased as compared with the casethat both the blade bodies 2, 3 are joined only in the vicinity of thelower end of the clearance 10. Further, when an impeller is producedwith the use of such a hollow blade 1 formed of both the blade bodies 2and 3, operational reliability can be ensured.

In the present embodiment, an amount of deformation of each of theconvex parts 23, 32 through the application of pressure by the horn 16is set at a value approximately identical to the height of the convexpart 23, 32. Accordingly, as shown in FIG. 3, when the joint work iscompleted, no impression of the convex parts 23, 32 is left on thesurface 1e of the hollow blade 1 and an approximate flush surface isformed from the back face 2b of the first blade body 2 to the surface 3aof the second blade body 3, thereby ensuring excellent smoothness. As aresult, when an impeller is produced with the use of the hollow blade 1,noise production during the running of the impeller can be reduced ascompared with the conventional case that an impression due to the jointwork is left on the blade surface, thereby realizing a quiet run of theimpeller.

Further, the hollow blade 1 manufactured according to the presentembodiment is subjected to a post-manufacturing quality inspection inwhich the joint state of the first and second blade bodies 2, 3 isverified. In the hollow blade 1 of the present embodiment, the convexparts 23, 32 having been formed on the first and second blade bodies 2,3 prior to the joint work are eliminated by deformation under pressureduring the joint work. Accordingly, in the quality inspection, aninspector can check the state of the first resin melting part 41 insidethe hollow blade 1 with ease and reliability through a visual check forthe convex parts 23, 32 from outside. Thus, the joint state can beverified with ease and reliability thereby ensuring efficiency andreliability of the quality inspection.

INDUSTRIAL APPLICABILITY

As described so far, according to a method of manufacturing a hollowblade of the invention and a hollow blade manufactured by the method,the joint state can be readily verified and high joint strength can beobtained. Such a hollow blade is suitable for use in a low-noiseimpeller.

What is claimed is:
 1. A method of manufacturing a hollow blade wherebyfirst and second resin-made blade bodies formed by injection molding areput together and are joined by welding by means of an ultrasonic weldingdevice to form a hollow blade internally provided with a hollow part,comprising the steps of:injection-molding the first and second bladebodies, forming respective convex parts swelling from respectivesurfaces of the first and second blade bodies at positions contiguouswith and opposed to each other when both the blade bodies are puttogether; placing a horn of the ultrasonic welding device at a positionthat the horn crosses both the convex parts to come into contact withthe top surfaces of the convex parts while pressing them at the sametime and then, in this state, operating the ultrasonic welding device;and welding contact surfaces of the first and second blade bodies whichextend in a direction approximately orthogonal to a direction of puttingtogether both the blade bodies at their portions corresponding to apressing direction of the horn, and concurrently deforming both theconvex parts by melting under pressure through the horn to tricklemelting resin of both the convex parts into a clearance between thefirst and second blade bodies so that both the blade bodies are welded,thereby joining both the blade bodies into one piece to form a hollowblade.
 2. A method of manufacturing a hollow blade according to claim 1,whereinan amount of deformation of each of the convex parts through theapplication of pressure by the horn is set at a value approximatelyidentical to the height of the convex part.
 3. A hollow blade in whichfirst and second blade bodies made of resin are put together to form ahollow part therebetween, whereinthe first and second blade bodies madeof resin in a state of being put together are joined by welding at theircontact parts and their opposed parts forming a clearance created whenthe first and second blade bodies are put together, and a welded part atthe clearance between the first and second blade bodies is formed suchthat the surface of the welded part is approximately coplanar with asurface of the hollow blade comprising the surfaces of the first andsecond blade bodies.